The present invention is, in general, directed to fuel cells and methods of their manufacture and use. More particularly, the present invention relates to fuel cells capable of operation by electrolyzing compounds in a biological system and methods of their manufacture and use.
There is interest in a variety of techniques for providing intermittent or continuous electrical power from a power source that utilizes constituents of the environment. In the context of devices implanted in a human or animal, there is a desire to find an energy source that utilizes the body""s own chemicals for providing electrical power to the device. This typically includes a mechanism for converting energy stored in chemical compounds in the body to electrical energy. Such devices have been difficult to prepare and implement.
In outdoor situations, solar energy, wind energy, and mechanical vibrations have been used to provide power from the environment. However, because of the diffuse nature of these sources of energy, devices with relatively large footprints are needed to provide the desired energy. Furthermore, these sources of energy are often intermittent and may not be available in all situations. Another potential source of energy is available from chemical energy stored in plants or their residue.
Electrochemical fuel cells have been developed to convert energy stored in chemical compounds to electrical energy. After nearly 50 years of research and development, however, only the hydrogen anode/oxygen cathode fuel cell operates at ambient temperatures. Fuel cells that operate using organic compounds have not been developed, at least in part, because the surfaces of electrocatalysts for the oxidation of organic compounds have not been stabilized. Fouling by intermediate oxidation products, that are strongly bound to the active sites of the catalysts, causes loss of electrocatalyst activity. Thus, there is a need for the development of electrochemical fuel cells that have electrocatalysts that are resistant to fouling and that can operate using compounds found in biological systems.
Generally, the present invention relates to fuel cells that operate using fuels from biological systems. One embodiment is a fuel cell having an anode and a cathode. Anode enzyme is disposed on the anode and the anode is configured and arranged to electrooxidize an anode reductant in the presence of the anode enzyme. Likewise, cathode enzyme is disposed on the cathode and the cathode is configured and arranged to electroreduce a cathode oxidant in the presence of the cathode enzyme. In addition, anode redox hydrogel may be disposed on the anode to transduce a current between the anode and the anode enzyme and cathode redox hydrogel may be disposed on the cathode to transduce a current between the cathode and the cathode enzyme.
Electrical energy is produced in the fuel cells of the present invention as a biological fluid containing the anode reductant, such as, for example, sugars, alcohols, carboxylic acids, carbohydrates, starches, and cellulose, and the cathode oxidant, such as, for example, O2, flows through the cell. The electrical energy produced by the fuel cell can be stored or used to power an attached device.
Another embodiment of the invention is a method of generating electrical power in a biological system by inserting an anode and a cathode into the biological system. A biochemical anode reductant is electrooxidized on the anode in the presence of an anode enzyme. And a cathode oxidant is electrodreduced on the cathode, spaced apart form the anode, in the presence of a cathode enzyme.
The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify these embodiments.